(genetics) The opposite orientation of the two complementary strands or deoxyribonucleic acid, 5′ to 3′ and 3′ to 5′.
(mathematics) Property of two nonzero vectors in a vector space over the real numbers such that one vector equals the product of the other vector and a negative number.
(physics) Property of two displacements or other vectors which lie along parallel lines but point in opposite directions.

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